No, he wasn't. They went overboard with bringing people back because Roman wasn't a star. They gave him damn-near everything and he still wasn't accepted by the crowd. He finally beat Cena in merch after Cena more-or-less retired and stopped shilling shyt. He wasn't over.
Cena, was a star even though people turned on him pretty quickly into his big run. It became his character. Roman, never had a character other than, "Hey, remember the Shield."
Seth has a WOAT voice. Dude sounds like a whiny teen. And he always came off as trying too hard to be an Omega/Tana hybrid without realizing the nuances and little things that both those guys do. But I agree, out of the three he could've been the most over if they gave him that preteen Jeff Hardy demo.
Dean was never going to work in scripted WWE. His biggest strength was promos and once Shield disbanded they made him, "LOL HE's WACKY AND CRAZY" instead of someone who was unhinged. In CZW he was the bum that you would cross the other street to get away from because he might try some shyt. Take that, and then his wrestling... I mean, for years Cena had the shyttiest punches until I saw Dean's "flurries".
Overall, It was smart of them to try to push three guys (or one guy, while the other guys get screen time), but in hindsight, it didn't work as effectively as it should've. These guys were the main character of WWE for 4 years, they should be above everyone on the roster and the fact is, they all feel like just another person on the roster.
Cena, Austin, Rock never felt like that. They always felt above the roster and as their own men. I thought that the last good thing WWE did was book Joe vs Brock because it was the last time that people thought something felt real. Joe knows how to do that UFC-style promo and get the best of Brock. Joe came off as a dude that didn't give a shyt about petty shyt and was all about the smoke from anyone on the roster, it felt genuine. Shield always felt like we were being forced into liking them, which is why Roman didn't get as over as he should've.